From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759480AbZFWLob (ORCPT ); Tue, 23 Jun 2009 07:44:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758097AbZFWLoS (ORCPT ); Tue, 23 Jun 2009 07:44:18 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:56727 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757368AbZFWLoQ (ORCPT ); Tue, 23 Jun 2009 07:44:16 -0400 From: KOSAKI Motohiro To: Jens Axboe Subject: Re: merging the per-bdi writeback patchset Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , Linus Torvalds , Linux Kernel , hch@infradead.org In-Reply-To: <20090623112849.GA31415@kernel.dk> References: <20090623201225.223F.A69D9226@jp.fujitsu.com> <20090623112849.GA31415@kernel.dk> Message-Id: <20090623204119.2245.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 23 Jun 2009 20:44:16 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > > > Can you please make reproduce program and post mesurement result? > > > > I hope to mesure the same program on my box. > > > > > > For which issue? Lumpy writeout can often be observed just by doing > > > buffered writes to a bunch of files. > > > > Yes, I know current behavior is not perfectly optimal. > > but I haven't seen it cause serious issue. > > > > Then, I guess you have big degression workload, yes? if so, I hope to > > see it. > > Not really, I was just interested in making it more optimal. I work from > various fio job files, one case that is sped up greatly is doing random > writes with mmap to an otherwise buffered file. pdflush is both lumpy > and a lot slower there, even with many pdflush threads active. Looking > at disk utilization, pdflush doesn't manage more than ~80% for that. The > per-bdi writeback is completely smooth and gets about as close to 100% > utilization as possible (around ~98% there). And this is just one 1 > disk, the per-bdi writeback scales nicely upwards. pdflush falls flat. > > And then there are lots of cases where the performance is the same. For > many workloads, pdflush isn't really very active. > > > > > Plus, Can you please write more vervose patch description? your patch is a > > > > bit harder review. > > > > > > OK, I can probably improve on that. Do you mean the general description > > > of the patchset, or some of the individual patches? > > > > Hopefully both. honestly I haven't understand your main worryed issue. > > Does the above help? It's all about making the writeback more > consistent. So getting rid of the lumpy writeback and eliminating the > pdflush starvation were the prime motivators. ok, thanks. I try to review your patch series without any bias later.